Coating composition of an isocyanate terminated polyurethane a vinyl chloride polymer and polysiloxane

ABSTRACT

A COATING COMPOSITION THAT CONSISTS ESSENTIALLY OF AN ISOCYANATE TERMINAL POLYURETHANE, A VINYL CHLORIDE POLYMER AND A REATIVE POLYSILOXANE IS THE SUBJECT OF THIS INVENTION. THIS COATING COMPOSITION IS PARTICULARLY USEFUL FOR FORMING GLOSSY VAPOR PERMEABLE FINISHES ON NATURAL LEATHER AND SYNTHETIC MICROPOROUS CORIACEOUS SHEET MATERIALS THAT ARE FREE FROM SURFACE TACK.

United States Patent Int. Cl. C08g 41/04 Us. Cl. 260-827 11 Claims ABSTRACT OF THE DISCLOSURE A coating composition that consists essentially of an isocyanate terminated polyurethane, a vinyl chloride polymer and a reactive polysiloxane is the subject of this invention. This coating composition is particularly useful for forming glossy vapor permeable finishes on natural leather and synthetic microporous coriaceous sheet materials that are free from surface tack. I

CROSS-REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION This invention is concerned with a coating composition for vapor pemeable sheet materials useful for making shoe uppers, and in particular, sheet materials of this type which are highly glossy. These glossy materials are also used to make ladies handbags, purses, belts and other articles requiring strength, flexibility and durability.

A variety of coating compositions providing -a high gloss finish have been commercially available for several years. Most of these compositions are both non-porous'and' impervious to vapors and the remainder have vapor permeability values substantially less than the minimum. required for comfortable shoe uppers. Also, flexibility and scuff resistance of most of these compositions is so low that they soon crack or lose their glossy appearance, or both. 1 a

In addition, these compositions when dried possess a surface tack which causes, for example, shoe uppers to adhere to one another when the glossy surfaces are placed in contactwith each other as occurs when one walks or sits. This surface tack is not only disconcerting to the wearer of the shoes and increases the scufiing of the shoe, but is also dangerous. There is at least one instance recorded where a womans shoes have stuck together causing the wearer to fall and injure herself.

This invention provides a coating composition that provides a durable highly glossy non-porous vapor permeable finish on microporous sheet material free from these deficiencies of the prior art materials, in particular free from surface tack and is eminently suitable for shoe uppers, ladies handbags, belts and other high style accessorres.

' STATEMENT OF THE INVENTION The coating composition of this invention has a 5 to 25% by weight polymer solids content in an inert organic solvent of a polymer blend that consists essentially of (l) About 70 to 99.9% by weight based on the total weight of the polymer of the coating of an isocyanate terminated polyurethane which is the reaction product of an organic diisocyanate and an active hydrogen containing ice polymer which is either a poly(alkyleneether) glycol or a hydroxy terminated polyester;

(2) Up to 25% by weight based on the weight of the polymer of the coating of a vinyl chloride polymer; and (3) 0.1-1% by weight based on the weight of the polymer of said coating of a reactive polysiloxane of the wherein R is either -H or an alkyl group having 1-4 carbon atoms, R is either -NCO, -NH -H or OH and n is an integer sufliciently large to give said polysiloxane an inherent viscosity of 0.1-2.0 at 25 C.

DESCRIPTION OF THE INVENTION The term non-porous as used in describing this invention refers to a sheet material or a coating of a synthetic polymeric material free from visible pores (as viewed by the naked eye or with a microscope of up to 300x power), which polymeric material in the form of an unsupported film one mil thick does not contain a significant number of light scattering gas/polymer interfaces.

The term porous refers to coatings and sheet materials which do not meet the test of non-porosity as set forth above. Microporous refers to porous materials, the pores of which are not discernible to the naked eye.

The term glossy, as used to describe this invention, refers to a surface having a reflectance of at least 50% at 60? in accordance with ASTM Test No. D-523-62T. All of the products of this invention have at least this minimum degree of reflectance and some have a reflectance of over 94% on this basis. Preferably, the products of this invention have a 60 gloss of 80 to 98.

Water vapor permeability value of the novel sheet material for this invention is at least 600, preferably 1200 to about 2100, and preferably, higher. Water vapor permeability of the novel sheet material is determined by sealing the sheet on top of a cup containing CaCl This sealed cup is stored at 90% relative humidity and the weight increase due to moisture permeating through the materialis determined and the water vapor permeability is calculated in grams of water 100 square meters of material/hour fibrous substrate have a thickness of about 0.1 to about 1.5 mil, and preferably, about 0.2-0.4 mil. This coating can be applied as a single layer or several layers so long as the total thickness does not exceed about 1.5 mil. When the coating comprises more than one layer, these may be the same or different polymeric materials. In accordance with a particularly preferred embodiment of this invention, the coating consists of two layers, each of a difierent polymeric material and with the embossing step taking place between application of the coatings.

Coatings of polymeric materials can be applied to the microporous fibrous substrate by any convenient procedure such as dip coating, spray coating, roller coating, doctor blade coating, lamination or the like so long as the coating has a uniform thickness. These coatings may be clear, but are preferably, pigmented and it is a particularly surprising attribute of this invention that products having coatings containing as much as 70% pigments by weight exhibit a highly glossy appearance.

The glossy vapor permeable coating of this invention consists essentially of 70 to 99.9% by weight based on the total weight of the polymer of the coating, and preferably, 90-98%, by Weight, of an isocyanate terminated polyurethane. The isocyanate terminated polyurethane is the reaction product of an organic diisocyanate and an active hydrogen containing polymer material which is either a poly(alkyleneether) glycol or a hydroxy terminated polyester.

The preferred polyurethanes are prepared with at least a major portion of an aromatic, aliphatic or cycloaliphatic diisocyanates or mixtures thereof; for example, tolylene-Z,4-diisocyanate, tolylene 2,6 diisocyanate, mphenylene diisocyanate, biphenylene 4,4 diisocyanate, methylene bis-(4-phenyl isocyanate), 4-chloro-l,3-phenylene diisocyanate, naphthalene-1,5-diisocyanate, tetramethylene-1,4-diisocyanate, hexamethylene 1,6 diisocyanate, decamethylene-1,10-diisocyanate, cyclohexylene- 1,4-diisocyanate, methylene bis-(4-cyclohexyl isocyanate) and tetrahydronaphthalene diisocyanate. Arylene diisocyanates, such as tolylene-2,4-diisocyanate and tolylene- 2,6-diisocyanate, are preferred.

The poly(alkyleneether) glycols used for the preferred polyurethanes contain C -C alkylene segments. The most useful polyglycols have a molecular weight of 300 to 5000, preferably 400 to 2000; some of these polyglycols are, for example, polyethyleneether glycol, polypropyleneether glycol, polytetramethyleneether glycol, polyhexamethyleneether glycol, polydecamethyleneether glycol, polydodecamethyleneether glycol, and mixtures thereof. Polyglycols containing several different radicals in the molecular chain, such as the compound wherein n is an integer greater than 1, can also be used.

One preferred polymeric material useful in forming glossy non-porous vapor permeable coatings in accordance with this invention is the polyetherurethane formed by reacting poly(propyleneether) glycol, molecular weight of about 1000, with a mixture of 2,4- and 2,6-toluene diisocyanate in a solvent, such as Cellosolve acetate. The resulting isocyanate terminated prepolymer is then cross-linked with water in the presence of dibutyltin dilaurate dissolved in cyclohexanone for coating purposes.

Hydroxyl terminated polyesters can be used instead of or in conjunction with the poly(alkyleneether) glycols, particularly those formed by reacting acids, esters or acid halides with glycols. Suitable glycols are polyalkylene glycols, such as n1ethylene-, ethylene-, propylene-, tetramethylene-, decamethylene glycol; substituted polyalkylene glycols, such as 2,2-dimethyl-1,3-propanediol; cyclic glycols, such as cyclohexanediol and aromatic glycols, such as Xylylene glycol. These glycols are reacted with aliphatic, cycloaliphatic or aromatic dicarboxylic acids or lower alkyl esters or ester forming derivatives to produce relatively low molecular weight polymers and molecular weights like those indicated for the polyalkyleneether glycols. Acids for preparing such polyesters are succinic, adipic, suberic, sebacic, phthalic, terephthalic, isophthalic and hexahydroterephthalic acids and the alkyl and halogen substituted derivatives of the acids.

A highly useful and preferred polyesterurethane for preparing the glossy non-porous vapor permeable coatings of this invention is prepared in accordance with Schollenberger US. Pat. 2,871,218, issued Jan. 27, 1959, and the disclosure of this patent is hereby incorporated into this specification and made a part thereof as illustrating useful polymeric coating materials.

One particularly useful type of polyesterurethane for the glossy coatings of this invention is prepared by reacting (1) a linear hydroxyl terminated polyester of a 4-10' carbon atom saturated aliphatic glycol and a saturated aliphatic dicarboxylic acid or an anhydride thereof, with (2) a phenyl diisocyanate, and (3) saturated aliphatic glycol having 4-10 carbon atoms. One preferred polyurethane of this type for use as the glossy coatingis the reaction product of hydroxyl terminated poly(tetrameth- 4 ylene adipate), diphenyl methane-p,p-diisocyanate and 1, 4-butane diol.

Up to about 25% by weight, based on the total weight of the film-forming polymer, of a vinyl chloride polymer is used in the glossy vapor permeable coating of this invention. For best results, about 2-10% by weight vinyl chloride polymer is used. The term vinyl chloride polymer is used herein in a broad sense and includes homopolymers of vinyl chloride, copolymers of vinyl chloride, containing at least 70% by Weight of vinyl chloride, as well as mixtures of homopolymers and copolymers of vinyl chloride. Monomers which are polymeriza-ble with vinyl chloride to form copolymers useful in this invention are, for example, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylonitrile and maleic, fumaric and acrylic esters. One preferred copolymer contains -90% by weight vinyl chloride and 2010% by weight vinyl acetate.

The reactive polysiloxane useful for forming the glossy coating of this invention is present in about 0.1-1.0% by weight, based on the weight of the film-forming polymer, and preferably for best results is present in about 0.2-0.5% by Weight. The polysiloxane has reactive end groups which may be either -H, --NCO, -OH or -NH which chemically bond the polysiloxane to the polyurethane used in the coating of the novel sheet material of this invention. Preferably, the reactive end group is NH The polysiloxanes useful for forming the glossy coating of this invention are of the following formula:

wherein R is either H, or an alkyl group of 1-4 carbon atoms, R is the aforementioned reactive end group and n is an integer sufiicient to give an inherent viscosity at 25 C. of about 0.1-2.0, preferably 0.5 to 1.0. Preferably, for best results, R is CH, and R is (CH NH Any of the well known pigments, extender pigments and dyes can be added to the polymer to form the glossy coating of this invention to give the desired color to the product. About 10-50% by volume pigment, and preferably, 15-25% by volume pigment, can be used. Typically useful pigments are, for example, metal oxides, such as titanium dioxide, metal hydroxides, chromates, silicates, sulfides, sulfates, carbonates, carbon blacks, organic dyes, such as fl-copper phthalocyanine, lakes and metal flake pigments.

The solvents used for the novel coating composition used to form a glossy sheet material should be of such a character as not to degrade the microporous fibrous substrate. Coating compositions contain about 5-25% by weight polymer solids, i.e., the aforementioned blend of polyurethane, vinyl chloride polymer and polysiloxane used for the glossy coating. Preferably, a coating composition of about 10-20% by Weight polymer solids are used. Typically useful solvents that can be used with a microporous sheet material of a polyurethane are methyl ethyl ketone, tetrahydrofuran, cyclohexanone, acetone, mixtures of toluene/ ethanol, benzene/methanol, toluene/ isopropyl alcohol, benzene/t-butyl alcohol, xylene/n-butyl alcohol, xylene/ methyl Cellosolve, xylene Cellosolve, benzene/methy isobutyl carbinol, methylene chloride/carbitol, methylene chloride/n-butanol and the like.

After the microporous fibrous substrate is coated with the above described composition, the glossy surface on the novel sheet material of this invention is obtained preferably by embossing the coated surface in accordance with the processes of U.S. Pat. 2,801,949 to Bateman Aug. 6, 1957, and US. Pat. 3,157,723 to Hochberg Nov. 17, 1964. These enhance the degree of gloss of the sheet material and improve its jetness. In accordance with this procedure, a sheet material having a polymeric coating is placed in contact with a smooth film of cellophane,

cellulose acetate, polyethylene terephthalate or the like and passed through the nip of the embossing cylinder and the pressure bladder described in U.S. Pat. 3,157,723 with the smooth film in contact with the coating of the fabric. The pressure roller in contact with the film can be engraved orsmooth depending upon whether a pattern is desired on the surface of the final product. In any event, the smooth film by being in contact with the polymeric coating of the microporous material during passage between the aforementioned nip of theembossing roller and the pressure bladder imparts to the coating an extremely high gloss which is revealed in all its brilliance upon the removal of the film from the coated microporous substrate. So far as is known, no other convenient means is available at the present time to produce a vapor permeable non-porous synthetic polymeric coated material having such a high gloss. These products are eminently suitable for making shoe uppers and other accessories.

The microporous fibrous substrate used to form the glossy sheet material can be natural leatheror a synthetic microporous sheet material. Preferably, a synthetic microporous fibrous substrate is used which preferably is formed by the process of one of the following patents which are hereby incorporated by reference:

Johnston et al. U.S. 3,000,757, issued Sept. 19, 1960; Holden U.S. 3,100,721, issued Aug. 13, 1963; Yuan 3,190,766, issued June 22, 1 965; Holden U.S. 3,208,875, issued Sept. 28, 1965; Hulslander et al. U.S. 3,284,274, issued Nov. 8, 1966; Patsis U.S. 3,364,098, issued Jan. 16, 1968. One preferred microporous sheet material is prepared according to U.S. patent application, Ser. No. 634,465, to Bateman, filed Apr. 28, 1967, now U.S. Pat. No. 3,520,765, and the disclosure of this application is hereby incorporated by reference.

The examples which follow illustrate the invention. All quantities are on a weight basis unless otherwise indicated. v I 0.

Example 1 Coating Composition A is prepared by blending together the following ingredients:

' Parts by weight Methyl ethyl ketone 535.0 Vinyl chloride copolymer solution(20% polymer solids of vinyl chloride/vinyl acetate, weight The poly-siloxane is blended with methyl ethyl ketone and the vinyl chloride is slowly added with constant agitation. The urethane polymer solution is then added and the ingredients are mixed for minutes. The dibutyl tin laurate solution is added and the ingredients are thoroughly blended for 5 minutes. The resulting coating composition has a polymer solids content of about 14% Coating Composition B which is capable of forming a glossy vapor permeable coating is prepared 'by dissolving 4.5 parts by weight of a polyesterurethane and about 2 parts by weight of a pigment composition in about 93.5 parts by Weight of tetrahydrofuran. The polyesterurethane is a commercially available product from the B. F. Goodrich Company under the trademark Estane 5707-Fl, and is believed to be prepared according to the process of U.S. Pat. 2,871,218, and is believed to be the reaction product of hydroxyl terminated poly(tetramethylene adipate), diphenylmethane-p,p'-diisocyanate and 1,4-butane diol. The pigment composition consists of 20% by weight of very finely ground carbon black having an average particle size of about 0.1 micron, 12% by weight dibutylphthalate and 68% by weight of a copolymer of vinyl chloride/vinyl acetate, weight ratio /15.

A roll of microporous polyurethane foundation material about 42 inches wide is made in accordance Wth the teachings in Example 1 of U.S. patent application, Ser. No. 634,465, to Bateman, filed Apr. 28, 1967. The resulting product is a porous impregnated non-woven web about 50 mils thick of 0.5 denier heat shrunk polyethylene terephthalate fibers impregnated with a microporous polyurethane polymer have an interlayer fabric and that has a uniform and firmly adhered layer on one side about 10 mils thick of a microporous polyurethane polymer.

The microporous foundation material is then dyed black with Nigrasine dye (C.I. Acid Black 2) according to the process of Manwaring U.S. Pat. 3,337,289, issued Aug. 22, 1967. The microporous sheet material is dipcoated "with Coating Composition B. The sheet material is passed around a roll in the dip tank containing, Coating Composition B With the substrate side contacting the roll and the microporous polyurethane surface exposed to the coating composition. The manner in which the material wraps around the roll and the level of the coating composition is selected so the mixture contacts only the microporous coated side and edges of the sheet material. A coating line speed of about 8 yards per minute is used which results in a coating weighing about 0 .20 ounce per square yard (dry weight) after the material is air dried in an oven at about 115 C.

The coated material is then embossed by placing a sheet of polyethylene terephthalate in contact with the dried coating and pressing it according to the process of U.S. =Pat. 2,801,949 and using the equipment of Hochberg, U.S. Pat. 3,157,723. The resulting sheet material has 'a glossy microporous surface. The coated sheet material is subjected to the following tests and the results of these tests are recorded in Table I.

Bally Flexometer test.-The Bally Flexometer provides a rolling, folding type of action in which a metal finger pushes into the sample from the back while the sample is rocked up and down. The samples are inspected after 40,000 flexes. Appearance of cracks in the finish and also failure of actual finish by flaking, generally around the areawhere the metal finger is pushed into the material, is recorded.

Water vapor permeability determinations-Permeability of the above prepared finished microporous polyurethane sheet material is determined by sealing the sheet on the top of a cup containing CaCl and by determining the weight increase of CaCl due to moisture pickup in the cup. The cup is stored at RH. in a constant temperature room at 72 F. for a two-hour period. The Water vapor permeability of the sheet is then calculated in grams of water per hour per square meters of material.

Surface tack.-is the force in grams necessary to separate two surfaces of material placed in contact with each other. The instrument is a Dunlap Tachmeter which consists of a rotatable wheel mounted on a frame assembly which holds a test sample 6 inches x /2 inch around its circumference. A calibrated spring which measures the force necessary to free the test strip on the Wheel from a sample is attached to the Wheel and the frame of the instrument. An aperture in the base of the frame assembly allows contact between the test strip on the Wheel and the sample of material on which the instrument is standing. A scale measuring the extension of the calibrated spring is marked on the cylindrical body of the frame and a rider attached to the frame indicates the tack in grams on the scale after the test samples are separated. The

wheel carrying the test strip is rotated 10 times and the instrument is moved over the test sample and an average value is determined to obtain statistically meaningful results.

Gloss test.-The gloss at 60 of each of the coated sheets is measured on a Glossimeter Model J-3, manufactured by Lockwood and McLoric', Inc., in accordance with ASTM Test No. D-523-64-T.

Coating Composition A is applied on the glossy side of the microporous sheet over Coating Composition B by the same procedure as used for applying Coating Composition B. The coated sheet is dried in an oven at about 150 C. to give a clear topcoating of about 0.2 ounce per square yard. The resulting sheet material is measured for water vapor permeability, gloss, surface-tack and flexibility according to the aforementioned methods and the results are recorded in Table I. The novel topcoating composition of this invention gives a material that is essentially tack-free but retains the gloss, flexibility and permeability of the material coated with the conventional Coating Composition B.

Example 2 Coating Composition C is prepared by blending Coating Composition B with about 0.2% by weight based on the weight of the polymer of the -NCO terminated polysiloxane having an inherent viscosity at 25 C, of about 0.5. Coating Composition C is applied to the dyed uncoated microporous foundation material described in Example 1 at about 0.2 ounce per square yard (dry weight) using the coating procedure of Example 1. The resulting sheet material has about the same high level of gloss, excellent flexibility and is permeable to water vapor as the material of Example 1 which is coated with Composition B as shown in Table I. The material coated with Composition C is essentially free from surface tack while the material of Example 1 coated with Composition B has a high level of surface tack.

Example 3 Coating Composition D is formulated using the same ingredients and formulating procedure as used in Example 1 to form Coating Composition A except a H terminated polysiloxane having an inherent viscosity at 25 C. of about 0.5 was substituted for the NCO terminated polysiloxane of Example 1.

The resulting Coating Composition D is coated onto a microporous foundation material that is coated with Composition B as described in Example 1. The resulting sheet material has a coating of about 0.2 ounce per square yard of Composition D (dry basis). The sheet is tested, as in Example 1, for gloss, water vapor permeability, flexibility and surface tack. The results of these tests which are recorded in Table I indicate that the microporous sheet coated with Composition D has similar excellent physical characteristics as the coated microporous sheet material of Example 1.

Example 4 Coating Composition E is formulated using the same ingredients and formulating procedure as used in Example 1 to form Coating Composition A except 21 NH; terminated polysiloxane having an inherent viscosity at 25 C. of about 0.5 was substituted for the -NCO terminated polysiloxane of Example 1.

The resulting Coating Composition E is coated onto a microporous foundation material that is coated with Composition B as described in Example 1. The resulting sheet material has a coating of about 0.2 ounce per square yard of Composition E (dry basis). The sheet is tested as in Example 1, for gloss, water vapor permeability, flexibility and surface tack. The results of these tests which are recorded in Table I indicate that the microporous sheet coated with Composition E has similar excellent physical characteristics as the coated microporous sheet material of Example 1.

Example 5 Coating Composition F is formulated using the same ingredients and formulating procedure as used in Exam- 8 ple 1 to form Coating Composition A except a -OH terminated polysiloxane having an inherent viscosity at 25 C. of about 0.5 was substituted for the NCO terminated polysiloxane of Example 1.

The resulting Coating Composition F is coated onto a microporous foundation material that is coated with- Composition B as described in Example 1. The resulting sheet material has a coating of about 0.2 ounce per square yard of Composition F (dry basis). The sheet is tested,

as in Example 1, for gloss, water vapor permeability,-

flexibility and surface tack. The results of these tests which are recorded in Table I indicate that the microporous sheet coated with Composition F has similar excellent physical characteristics as the coated microporous sheet material of Example 1.

tion F Rating system for Bally flex: 1=No cracks in finish; 2=Mierocracks in finish; 3=\'isual cracks and microcracks in finish without finish failure; 4=Severe visual cracks with failure of finish; 5=Severe vlsual cracks and gfiigplete failure of finish with flaking; of the finish from the microporous What is claimed is:

1. A coating composition having about 5 to about 25 percent by weight of polymer solids in an inert organic solvent of a polymer blend which consists essentially of (a) about 70 to 99.9% by weight based on the total weight of the polymer of an isocyanate terminated polyurethane which is the reaction product of an organic diisocyanate and an active hydrogen containing polymer selected from the group consisting of poly-(alkyleneether) glycol and a hydroxy termi-v nated polyester; (b) up to 25% by weight based on the total Weight of the polymer of a vinyl chloride polymer; and

(c) 0.1-1.0% by weight based on the weight of the polymer of a reactive polysiloxane of the formula urethane, 2-10% by weight of said vinyl chloride polymer and 0.2-0.5% by Weight of said polysiloxane.

3. The coating composition of claim 2 in which R is hydrogen.

4. The coating composition of claim 3 in which the polyurethane is the reaction product of an aromatic diisocyanate and a poly(alkyleneether) glycol having a weight average molecular weight of about 300-5000.

5. The coating composition of claim 4 in which the" vinyl chloride polymer is a copolymer of about -90% by weight vinyl chloride and 20-10% by weight vinyl:

acetate.

6. The coating composition of claim 3 in which the polyurethane is the reaction product of an aromatic diisocyanate and a hydroxyl terminated polyester.

7. The coating composition of claim 6 in which the aromatic isocyanate is diphenyl methane-p,p-diisocyamate and the hydroxyl terminated polyester is poly(tetramethylene) adipate:

8. The coating composition of claim 1 in which the polymer blend consists essentially of 9098% by weight of an isocyanate terminated polyurethane of an aromatic diisocyanate and a poly(alkyleneether) glycol, 2-10% by weight of a vinyl chloride polymer and 0.2-0.5 by weight of polysiloxane where R is H and R is NCO.

9. The coating composition of claim 1 in which the polymer consists essentially of 90-98% by weight of an isocyanate terminated polyurethane of an aromatic diisocyanate and a poly(alkyleneether) glycol, 2-10% by weight of a vinyl chloride polymer and 02-05% by weight of polysiloxane where R is H and R is -NH 10. The coating composition of claim 1 in which the polymer blend consists essentially of 90-98% by Weight of an isocyanate terminated polyurethane of an aromatic diisocyanate and a poly(alkyleneether) glycol, 2-10% by Weight of a vinyl chloride polymer and 02-05% by weight of polysiloxane wherein R is H and R is H.

11. The coating composition of claim 1 in which the 10 polymer blend consists essentially of 9098% by weight of an isocyanate terminated polyurethane of an aromatic diisocyanate and a poly(alkyleneether) glycol, 2-10% by weight of a vinyl chloride polymer and 0.2-0.5% by weight of polysiloxane wherein R is H and R is --OH.

References Cited UNITED STATES PATENTS 2,871,218 1/1959 Schollenberger 260-858 3,203,919 8/1965 Brachman 260-296 3,298,856 1/ 1967 Harding 117-76 3,450,791 6/1969 Sekmakas et a1. 260--826 3,481,767 12/1969 Craven et al. 117-76 SAMUEL H. BLECH, Primary Examiner US. Cl. X.R.

117-11, 76 F, 76 R, 135.5, 142, 161 KP, 161 ZA; 260-23 TN, 23 XA, 30.4 N, 30.4 $13, 31.4 R, 32.8 N, 32.8 $13, 33.2 $13, 33.4 $13, 33.4 UR, 37 SB, 40 TN, 41 R, A, B, c, 824 

